JOIN(setofdatasets, joincondition, transform, SORTED( fields) [, jointype] [, UNORDERED | ORDERED( bool ) ] [, STABLE | UNSTABLE ] [, PARALLEL [ ( numthreads ) ] ] [, ALGORITHM( name ) ] )

The second form of JOIN is similar to the MERGEJOIN function in that it takes a SET OF DATASETs as its first parameter. This allows the possibility of joining more than two datasets in a single operation.